Abstract: Fluid flow properties often dictate the performance of processing operations. The present invention relates to a system for evaluating properties of a fluid flowing in a pipe. A test cell (20) which includes two parallel surfaces (5, 6) which are positioned in the flow. One of the surfaces is moveable relative to the other, to a position in close proximity to the other, to create a stagnant flow region between the surfaces. The system further includes a test input device (10) to apply input motion to one of the surfaces, and a test output device (13) to measure output motions from the cell in response to input motions. Furthermore, the system includes a processing device (9) to calculate rheological parameters of the fluid from signals produced from the test input and test output device. There is also a process for evaluating properties of a flowing fluid.